Plugging the leaks

'There's a lot to get done over the summer'

WORK STATIONS: From left, Jacob Birch and Derek Alston examine a map outlining the details of the Tekapo canal repair work.

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Repairing the Tekapo canals is one of the biggest work projects of its kind in several decades. Timaru Herald reporter Matthew Littlewood and photographer Mytchall Bransgrove were invited for a site visit this week.

Imagine if you needed to plug your bathtub after it started to leak. Now multiply this by several thousand.

Click on the photo for more images from the canals.

That's the sort of job that has to be completed during the next two summers to fix the leaking Tekapo hydro canals.

The project requires several hundred thousand tonnes of earth to be moved, more than 200 Olympic-sized swimming pools of water drained (and then refilled) from the canals, and nearly 8 kilometres of the canal to be lined with special material from Europe. This summer and the next, there will be more than 150 workers on the site. Genesis Energy, which owns the structure, estimates the repair work will cost more than $125 million.

This week we were able to get a closer look at the work. After we were issued with the hard hats, high-vis vests and a compulsory safety debrief from Genesis's engineering services manager Michael Campbell, we were led to the site. Earthmoving vehicles, cranes and other heavy machinery surround us.

"It's hard not to be a happy worker when you get to look at that view every day," Campbell says, pointing to the perfect view of Aoraki-Mt Cook.

The 27km canal structure was built to connect the Tekapo A and B power stations in the 1970s, but in recent years, it has suffered serious wear and tear.

In 2008, state-owned generator Meridian undertook urgent repair work after it discovered major leaks caused by erosion, but even that was only a temporary measure. Then in 2011, the Government ordered rival state-owned Genesis to buy the Tekapo power stations from Meridian for $800 million.

Officially, repair work began on January 9, after the canals were drained of all their water. Temporary holding structures, known as cofferdams, will remain in place until the canals are refilled on April 22. Campbell says it took a day to install each of the cofferdams and it will take a day to remove them. Similarly, the refilling of the canal takes three days.

"That means we don't actually have much time to do this work. There's a lot to get done over the summer. Genesis can't exactly delay the re-filling, there are commercial considerations," Campbell says.

European firm Carpi-Tech won the contract for the special lining material, and has sent about 50 of its workers to the site. Many come from Hungary and Italy, and will be staying in Twizel and Tekapo. Fulton Hogan has about 150 workers tasked with earthmoving and other industrial work. Genesis bought a neighbouring farmer's land to accommodate the porta-cabins.

Campbell says about 8km of the canal needs to be lined and about two-thirds of the job will be completed this summer.

"The material is in 100m strips; it all needs to be welded together. It's surprisingly detailed. These people are the best in the world at this sort of job."

Next summer, the major work will be on repairing the section known as the Maryburn Fill.

"Logistically speaking, it's a pretty complex job - but so is most of what will be done," Campbell says.

It has also affected the neighbouring Mt Cook Alpine Salmon business, which farms on the hydro canals. More than 400,000 fish had to be "re-homed" (into rafts on the Ruataniwha or Ohau canals) or harvested after the canals were drained.

Meanwhile, most of the public access to the canal road has been blocked off. However, you can still drive over the State Highway 8 bridge.

Campbell says the project is a one-in- 50 year event. All things going to plan, this should futureproof the canals for decades to come.